import java.util.Scanner;
public class  fenshu {
    public static void main(String[] args) {
                Scanner in = new Scanner(System.in);
                int[] grade = new int[5];
                for(int i=0; i<grade.length; i++){
                      grade[i] = in.nextInt();
                 }       

                RR rr = new RT(grade);
                double dd = rr.mark();
                System.out.printf("%.2f",dd);    
    }
}
abstract class RR{
   int[] grade;
   public RR(int[] grade){
      this.grade = grade;
   }
   public abstract double mark();
}
class RT extends RR{     
  public RT(int[] grade){
    super(grade);
  }
  public double mark(){
    double x = (grade[1]+grade[2]+grade[3])/3;
    return x;
  }

}